Portal is a puzzle-platformer franchise developed by Valve, which is set in the Half-Life universe. The series relies on solving puzzles with portals and has gained both critical and financial success.
There are currently two games in the series: Portal (which was released in 2007) and Portal 2 (which was released in 2011), both of which center on a human test subject (named Chell) who is forced to undergo a series of tests within the Aperture Science Enrichment Center by a psychotic artificial intelligence computer GLaDOS, who controls the facility.
Aperture Science was founded by Cave Johnson (voiced by J.K. Simmons) and originally sought to make shower curtains for the military, but its researchers happened upon the discovery of portal technology, and soon became a direct competitor with Black Mesa Research Facility (from the Half-Life series) for government funding.
Most of the tests involve using the "Aperture Science Handheld Portal Device" to create human-sized portals between two flat surfaces. Not only can the player-character and objects in the game world move through portals, their momentum is conserved, allowing complex "flinging" maneuvers to be used to cross wide gaps or perform other feats to reach the exit for each test chamber. A number of other mechanics, such as lasers, light bridges, tractor funnels, and turrets, exist to aid or hinder the player's goal to reach the exit.
The concept of Portal was born out of a student project from the DigiPen Institute of Technology. That project, called Narbacular Drop, formed the basis for the first game, while a second student project, called Tag: The Power of Paint, formed the basis of surface-altering "conversion gels" introduced in Portal 2.
The first game was released as part of a three-game compilation, The Orange Box, and though intended as a short bonus feature of the compilation, was instead considered the highlight of the three and received near-universal praise. Its success led to the creation of the much longer Portal 2, which included both single player and cooperative player modes.
In addition to innovative puzzle gameplay, both games are praised for their dark humor, dialogue, and voice acting.
